Combustion control for heating systems



Sept. 1, 1936.

' A. W. HOLMES COMBUSTION CONTROL. FOR HEATING SYSTEMS 2 Sheets-Sheet lhr/zvzzar Filed Aug. 30, 1952 Se t. 1, 1936. A. w. HOLMES COMBUSTIONCONTROL FOR HEATING SYSTEMS Filed Aug. 30, 1

Hull 3% 6 r x f f w A n m Patented Sept. 1, 1936 PATENT o-r-rlescomUsTioNooN'moL FOR HEATING SYSTEMS Albert w. Holmes, Providence, a. 1.Application August 30, 1932,-Serial No. 631,005' '6 Claims. (01. 110-75)My present invention relates totheheating art,

' and has particular reference to the 'control of combustion of handfired stoves, furnaces, and boilers.

, Careful study of the combustion of coal in the above hasd'isclosedthat approximately fourteen pounds of air must be supplied per pound ofcoal consumed, and that about one half must be supplied below the grateas primary air, and one half in the combustion space above the fire assecondary air, to ensure complete combustion.

. Complete combustion under usual operating conditions has been found torequire an initial or primary combustion, and a subordinate or sec- 5ondary combustion; the primary combustion occurring on the grate barsand in the fire bed, and

the secondary combustion occurring in the combustion space above thefire bed. Theprimary combustion requires a sufiicientsupply' of airunder the gratebars, and a sufficient temperature to" produce thedesired combustion; this is obtained by controlling the flow of airintothe ash pit, or'under thegrate bars,-and regulating the rate ofgasification of the coal in the fuel bed.

The secondary combustion'r'equires admission of a sufficient supply ofair to the combustion'space,

' a thorough mixture of this air with the gases from the fuel bed,sufiicient temperature to complete thecombustion, sufiicient space topermit the-necessary expansion of the gases during the combustionprocess, and control of the outflow so as to permit the combustion to becompleted.

Eficient'furnaceoperation thus requires accurate control of the primaryair, the secondaryair, and the speed of combustion; as the combustiblegases must'have sufiicient time in'the'firebox for completecombustion.Moreover, the secondary air shouldbe heated, and injected intothe combustion space 'so as to spread over the fuel bed'and thoroughly mix withthe gases ascending from the fuel bed.

It is the principal object of my invention to control the supply ofprimary air, secondary air, and the speed of combustionso as toobtainmaximum 45 efiiciency; Other objects of my invention are topreheat the secondary air and to inject the secondary air in many smallstreams over the fuel bed so as to thoroughly mix oxygen with thecombustible gases and complete the combustion.

With the above and other objects'and advanta'geous features in view, theinvention consists of an arrangement of parts more fully disclosed inthe detailed descriptionfollowing, in' conjunction with the accompanyingdrawings, and more 'spe-' cifically defined in' the claims appendedthereto.

' Referring to the drawings,

Fig. 1 is an elevation of a furnace equipped with the novel control;parts being broken away;

Fig. 2 is an elevation of the smoker pipe damper control;

unit;

Fig; 10 is a section on the line ltl'l3 of Fig. 9; Fig; 11 is a sectionon the line IE'-H of Fig. 10; and

Fig. 12 is a section on the line l2--|2'of Fig. 10.

Referring to the drawings, the furnace i5 is equipped with a fire boxunit It for controlling the admission of air to the combustion space ofthe firebox and for preheating the admitted air,

a damper unit H for controlling the outflow of H the flue gases, and adevice lflfor admitting air below the grate. These units are adapted tobe operated in unison by manual movement of a ratchet typecontrolleverl9, which movement is communicatedto the 'units by means of chains orthe like 28,2! and 22; counterweights 23, 24, and 25 are attached to thechains, in the usual manner, to normally hold the units in closedposition.

The damper unit is illustrated in Figs; 2 to 4, and includes a casting26 which is adapted to be mounted in the smoke pipe and is provided withside bosses to which a pivot stud plate 21 and a bearing plate 28 issecured, as by screws or bolts;

the damper 29 having a recess 39 to seat over the stud of the plate 21and having an operating shaft 3| extending through the bearing plate, anoperating handle 32 being secured'to the end thereof.

The bearing plate 28 is preferably formed with a guide quadrant 33,graduated in degrees, and having stops 3 3 at each end, whereby movement of the operating handle sets the damper at the desired degree ofopening, a stop 35 being provided for the damper to prevent completeclosure.

The smoke pipe device or damper unit is fur ther provided with a draftcontrol opening 36 contrblle'd by aslide' plate 31' which is slidablymounted on a guiderod 38"seated at its 'ends in end socket stands '39secured" to suitable bosses of the casting or smoke pipe 25. v The plate31 is shifted'by pressing two levers 40' which are pivotally mounted-onthe platetowards each other, the levers being spring pressed away fromeach other by a spring 'd Land having-pins 52- at their inner endsadapted to contact the rod 38 when released. r

The operation of the damper unit may now be explained. Movement of theoperating handle sets the main damper to the degree of opening, andmovement of the slide plate 31 controls the stack draft, and hence thespeed of combustion in the fuel bed. The. parts are designed forsimplicity of operation, are easily assembled, and cannot get out oforder under normal operating conditions. i

The fire box device is shown in Figs. 5 to 8, and includes an airadmission unit 43 andan air preheater unit 44, the two being secured inalign therethrough, an inlet, a fan shaped nose having ment to the fire,box door. The air admission unit includes a base 45 having a centraloutlet 46 and spaced air flow slots 41, an inlet shell 48' being securedto the base, as by a central screw, and having air admission openings49; a control valve 50 of plate type is rotatably mounted on the basebetween the base and the inlet shell, and has slots 5| adapted touncover-the slots' l'l in response to movement of the valve 50. Thevalve- 56 is shifted by movement of ,a'handle 52, which also functionsas a pointer and cooperates with a scale 53 mounted on the base andgraduated in degrees; limit stops are provided for the valve, thepreferred type including a pin 54 seated in the base and cooperatingrecesses or notches 55 in the valve59. q.

The ash pit air admission unit 18 is in'this instance similar inconstruction to the fire box air admission unit, but is larger. Theoperationv is identical, the valves being rotatedmanually by movement ofthe handle, or by securing the operating chain to the handle in anydesired and suitable manner, the rotation of the valve uncovering theflow slots tothe desired number of degrees as indicated on the scale andregulating the air inflow in accordance. 1

The air preheater unit is illustrated in detail in Figs. 9 to 1 2, andcomprises a casting 56 which extends into the furnace combustionchamberand through which the air 'isconveyed in a tortuousmanner beforeemerging from a fanshaped nose provided with many outlets or. jets-.:

The casting has vertical flues or: passages 51' through which the hotfurnace gases may readily circulate, and has an air inlet 58whichcommunicates with the upper portion, see Figs}? and 11,

the air passing between'the flues 5'! over the 'central partition 59 tothe forward end, and back along the outer sides, then down as showninFig. 10, and around the flues 5! to the outlets 60 which as shown aredrilled'to produce sharp edges to ensure maximum velocity of the airpassing into the combustion space and are arrangedafan shapetodistribute the heated air overthe entire fire box. The air'preheaterunit is preferably cast in two parts 6!, ,62, see Fig. 10, to simplifymanufacture.

The operation of the air preheater is as follows:

the admitted air is subjected tothe fire box heat. 7

in its tortuous passage, being initially heated along the upper portion,and then along the lower portion where it is exposed to the direct heatof the fire: the constant passing of the hot gases through the verticalflues 'orpassages facilitates transfer of heat from the hot gases to theair.

It is therefore evident that the novel construction provides an accuratecontrol of the supply of primary air, an accurate control of the supplyof secondary air, the secondary air being heated andjspread over thecoal bed, and an accurate control of the velocity and volume of theoutflowing flue gases, whereby the control of combustion is more exact,and the amount of excess air and the resultant heat loss is reduced to aminimum. 7

While I have described a specific constructional embodiment of myinvention, it is clear that changes in the arrangement, proportions, andrelative size of the parts, may be made to suit the requirements forparticular installations without departing from the spirit and the scopeof the invention as definedin the appended claims.

I claim:

1; An air preheater having a flue extending extending therethrough, apartition transverseto' said flues dividing the interior into an upperand a lower portion, an inlet communicating with the upper portion atone end, a plurality of outlet openings in the lower portion at theother end, and partitions for guiding the air passing into the upperportion between the flues to the other end, back around the flues to theentrance end, and into the lower portion to again pass through andaround the flues to the outlet openings;

3. An air preheater having a plurality offlues extending therethrough, apartition transverse to said flues dividing-the interior into an upperand alower portion, an inlet'communicating with the upper portion atone, end, the other end being formed as a fan shaped nose havingapluralityof outlet openings to spread'the outflowing air in a widearea, and partitions for guiding the air passe having a plurality offlues extending there-.

through, said air preheater having an inlet jcom'-. inunicating withsaid. flow'oontrol: opening, a partition transverse to saidfluesdividing'the'interior into an upper and a lower portion, theinlet.communicating with the. upper portion at one end, a plurality of outletopeningsrin the lower portionat the other end, and partitions forguiding the airpassing into the upper portion between the flues totheother end, back around the flues to the entrance end, andinto-thelowerportion to again pass through and around the flues to the outletopenings.

5. An air'preheater having aflue extending therethrough, an inlet, aplurality of outlet openings, and partitions directingthe flowing air ina tortuous passage 'aboutsaid flue to-s aid outlet openings, the crosssectional area of said tortuous.

- passage progressivelyincreasing towards the outlet openings.

6. An airpreheaterhaving two flues extending therethrough, an inlet, aplurality of outlet ope'n-. ings, andpartition means guidingthe flow ofair between the flues forwardly from said inlet, then backwardly aroundthe flues, then forwardly between and around the fluesto saidoutletopen-

